If it's in production, you'll need to make sure that you update all of your sql statements to accommodate the changes to the schema.

Without knowing more info on your data and how it's being gathered and populated in the db, it's hard to make any firm recommendations on a step-by-step process.

The easiest approach might be to add 2 additional fields (name and date) and use a stored procedure to split the data in the lastupdate field and put it into the new fields. Then use those fields in your query instead of the lastupdate field.